The present invention relates to utility vehicles, such as industrial or agricultural tractors. Particularly, the invention relates to tractors utilizing a rockshaft or three point hitch and an attachable rear-mounted implement.
Utility vehicles typically include an internal combustion engine, which delivers power to a transmission and ultimately to a wheel for traction, and also delivers power to pressurize hydraulic fluid, via one or more pumps, to operate hydraulic tools or implements.
In this regard, it is known to provide three hydraulic pumps driven from the engine. A first pump generates pressurized hydraulic fluid to charge a steering cylinder of the vehicle. A second pump generates pressurized hydraulic fluid to charge a power takeoff clutch pack and at least one hydraulic cylinder which operates a three point hitch or xe2x80x9crockshaft.xe2x80x9d The power takeoff is a shaft that is rotated by the vehicle transmission and is used for supplying rotational power to tools, such as mower decks, where rotation is required. The first and second pumps are driven by an auxiliary drive of the engine.
The third pump is usually fixed directly to the crankshaft of the engine and is used to charge pressurized hydraulic fluid to the loader and the backhoe hydraulic cylinders.
Typically, the first pump requires 1.4xcx9c8 horsepower, depending on steering demand and 6 GPM of hydraulic fluid. The second pump requires 1xcx9c9.5 horsepower, depending on demand from the auxiliary circuit, and 5.4 GPM of hydraulic fluid. The third pump requires 3.2xcx9c21.3 horsepower, depending on demand from loader or backhoe circuits and 12 GPM of hydraulic fluid. The engine typically delivers 42 horsepower.
When a backhoe is attached to the utility vehicle, the rockshaft is not needed, nor is it practically operable. The present inventors have recognized the desirability of disabling the rockshaft when a backhoe is attached to the utility vehicle. The present inventors have recognized the desirability of diverting hydraulic fluid that would otherwise supply the rockshaft, when the backhoe attachment is attached. Furthermore, the present inventors have recognized the desirability of using the circulating hydraulic fluid otherwise available to the rockshaft, to improve the effectiveness and efficiency of the utility vehicle.
The present inventors have recognized that a proper balance of available engine horsepower directed to the various tractor functions at the proper time is required for best operation of the machine. While the loader is in use, the transmission must necessarily also be in use simultaneously. As such, it is desirable to limit the available horsepower consumed in the operation of the loader while demands are placed on the transmission, to prevent engine stalling.
Conversely, the inventors have recognized that the backhoe is used without demand on the loader, transmission, rockshaft, or steering circuits. Furthermore, the backhoe has very high hydraulic power requirements. This is because in normal operation, 3 or more hydraulic cylinders (of a typical 7 total cylinders) may be in motion at any given time For this reason, the inventors have recognized that it would be desirable to utilize additional flow from tractor systems which are sitting idle while the backhoe is in use.
The present invention provides a method and apparatus for diverting pressurized hydraulic fluid, otherwise available to a utility vehicle rockshaft system, to be used by another hydraulic fluid powered implement on the utility vehicle. Particularly, the invention provides a method and apparatus for diverting pressurized hydraulic fluid from the rockshaft hydraulic system to be available to a backhoe attachment hydraulic system.
The method and apparatus of the invention are advantageously accomplished by use of a rockshaft disable switch. The switch is placed in a position such that installation of the backhoe attachment on the utility vehicle automatically changes the state of the switch.
The switch is connected to a solenoid operator that moves a valve spool to divert pressurized hydraulic fluid from a rockshaft control valve to other hydraulically operated tools, such as to the backhoe attachment. Additional hydraulic fluid available to the backhoe attachment allows for faster movements of the backhoe attachment operating hydraulic cylinders, and thus faster manipulations of the backhoe arms and backhoe bucket.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.